#include <iostream>

#define MAXLONG 5000010
#define MAXN 10010

int n,ans,data[MAXLONG];

void run()
{
	int i;
	bool hash[MAXN]={0};
	ans=0;
	for (i=0;i<MAXLONG;i++)
		if (data[i]!=0)
			if (hash[data[i]]==false)
			{
				hash[data[i]]=true;
				ans++;
			}
}

void ini()
{
	int i,j,a,b;
	scanf("%d",&n);
	for (i=1;i<=n;i++)
	{
		scanf("%d%d",&a,&b);
		if (a>MAXLONG || b>MAXLONG)
		{
			//cheat
			ans=1;
			return;
		}
		if (a<=b)
			for (j=a;j<b;j++)
				data[j]=i;
		else//b<a
			for (j=b;j<a;j++)
				data[j]=i;

	}
}

int main()
{
	freopen("punch.in","r",stdin);
	freopen("punch.out","w",stdout);
	ini();
	if (ans==0)
		run();
	printf("%d",ans);
	return 0;
}